'93 190E 2.3 - high idle - worst in neutral & park
 

Hi there,

I'm new to the forum.

I have a 1993 M-B 190E 2.3 (auto) that I have owned since new. It's been a brilliant car that has needed very little repair (outside of regular maintenance).

Two days ago I started experiencing a new issue.

When I stopped my car at the end of a ten minute drive and placed it into Park, the engine revved up to around 2500rpm. I thought that maybe the ECM might've been having a problem and needed resetting, so I went shopping and thought nothing of it.

Now in park and neutral it revs anywhere from 2500 - 3200 rpm, and in drive from 1000 - 1500 (causing some lurching at takeoff, and continued gas delivery when my foot's off the gas).

I replaced the throttle return spring last summer, and the throttle feel is still excellent, which leads me to believe that it is not a problem.

I've heard that this problem could be due to a problem with the throttle linkage, idle control valve or unit, or the microswitch engaged by the linkage.

Does anybody have any suggestions that could help me troubleshoot this issue?

I don't mind working 20 straight hours on the thing with my trusty Haynes guide, but I just bought an engagement ring, so I can't afford to take it to a shop for another couple of weeks!

Many, many thanks.

Russ

two more things...
 

A couple more things:

1. I'm in Toronto, and we are in a cold snap that started a few days ago. Think -15 Celsius.

2. My normal idle speed seems to be from 550 to around 750 rpm.

Thanks again!

Check for Vacuum leaks. Check all rubber vacuum connectors and also check to make sure all vacuum lines are connected. When there is a vacuum leak that is exactly the symptom. Could be something else but I would check there first.

Thanks Jamie
 

Thanks Jamie - I'm not the greatest under the hood (but learning). Where should I be looking test check for vacuum leaks?

All of the vacuum lines are pretty visable. Check all the rubber connectors for cracks, they get old and brittle and form cracks. Also just verify they are all connected somewhere. Then under the air cleaner you will see the Idle Air Control Valve and the Rubber bigger lines that connect that everywhere. Should be at least 4 pieces. Check them to make sure they are not hard and brittle. New ones are maybe 6 bucks a piece and very flexible. You could also clean the IACV as well with Carb Cleaner. And clean inside the Air Flow Meter as well, AFM....

Thanks again
 

Thanks again Jamie - I'll be checking this out over the weekend (with some help from a skilled friend).

I'll let you know how I make out.

Thanks!

Results
 

Turns out it was the valve under the air cleaner. From your posting I assume it was the Idle Air Control Valve. It was coated in grime and staying open. This was causing the high idle. My mechanic friend cleaned it up and things improved. He gave it a little tap with a hammer and things were perfect. I expect I'll have to change it soon, but it's bought me some time.

I really appreciate the help.

If it was coated with a varnishy, oily film devoid of particles of 'grime' , this just means it needs cleaning. Otherwise, you may have an air leak bypassing the air filter - not good, and should be fixed.

Steve

Also a good time to make sure all your throttle linkage is clean and properly lubricated.

Haasman